Time-resolved photoelectron imaging of the isolated deprotonated nucleotides
Time-resolved photoelectron imaging of the isolated deprotonated nucleotides
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DOI：
10.1039/c4sc01493f
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发表时间：
2014-01-01
期刊：
影响因子：
8.4
通讯作者：
Verlet, Jan R. R.
中科院分区：
文献类型：
--
作者：
Chatterley, Adam S.;West, Christopher W.;Verlet, Jan R. R.
使用时间分辨光电子能谱，在 4.66 eV 的紫外线激发后，监测了气相质量选择的核苷酸阴离子的激发态动力学。光谱表明，2'-脱氧鸟苷 5'-单磷酸阴离子 (dGMP(-)) 的动力学与腺苷核苷酸 (dAMP(-)) 的动力学非常相似，并且对溶剂不敏感。我们的结果与其他文献的比较表明，两个嘌呤碱基的核苷酸共享共同的弛豫途径，由此最初填充的 (1)pi pi* 态弛豫到基电子态，而不涉及任何其他中间电子态。在胸腺嘧啶和胞嘧啶的类似嘧啶核苷酸dTMP(-)和dCMP(-)中，没有观察到这种统一的机制。光激发的 dTMP(-) 的行为与分离的核碱基胸腺嘧啶非常相似，尽管具有较小的长寿命通道，但表现出快速弛豫至基电子态。另一方面，分离的 dCMP(-) 比其胞嘧啶核碱基寿命更长，因此看来核苷酸排列中糖和磷酸的存在导致了可用松弛途径的改变。核苷酸是 DNA 的基本单体构建块，我们的结果提供了重要的新基准数据，以加深对 DNA 暴露于紫外线时介导光损伤的分子机制的理解。
Using time-resolved photoelectron spectroscopy, the excited state dynamics of gas-phase mass-selected nucleotide anions have been monitored following UV excitation at 4.66 eV. The spectra reveal that the dynamics of the 2'-deoxyguanosine 5'-monophosphate anion (dGMP(-)) are very similar to those of the adenosine nucleotide (dAMP(-)) and are insensitive to solvent. Comparison of our results with other literature suggests that nucleotides of the two purine bases share a common relaxation pathway, whereby the initially populated (1)pi pi* states relax to the ground electronic state without involvement of any other intermediary electronic states. In the analogous pyrimidine nucleotides of thymine and cytosine, dTMP(-) and dCMP(-), no such unified mechanism is observed. Photoexcited dTMP(-) behaves much like the isolated nucleobase thymine, exhibiting rapid relaxation to the ground electronic state, although with a minor long-lived channel. On the other hand, isolated dCMP(-) is longer lived than its cytosine nucleobase, and hence it appears that the presence of the sugar and phosphate in the nucleotide arrangement leads to a modification of the available relaxation pathways. Nucleotides are the basic monomer building blocks of DNA and our results present important new benchmark data to develop an understanding of the molecular mechanism by which photodamage can be mediated when DNA is exposed to UV light.